Apparently, TurboTax did not add the necessary amendments to my tax return regarding the $400 work from home expenses.
Although I checked yes on box "Will you claim employment expenses for working at home due to COVID-19 for income on this T4? NEW!" TurboTax didn't prompt me to enter further information, so I left it as is believing it had manually added the $400. However, on line 22900 it shows as $0
How do I edit my return on TurboTax Online.
To get the work from home expenses deduction, you would also need to go through the Employment Expenses section of the interview. This FAQ shows where to claim your employment expenses in TurboTax Online: https://turbotax.community.intuit.ca/community/claims-deductions-donations/help/where-do-i-claim-my-employment-expenses-in-the-online-edition-of-turbotax/00/873421
FYI: You can claim $2 per day (up to $400) in employment expenses, which is a deduction from your taxable income, not a credit.
You can make changes after you have filed your tax return through the Canada Revenue Agency (CRA) or through ReFILE. This FAQ has more information: https://turbotax.community.intuit.ca/community/tax-return-amendment/help/i-have-filed-my-tax-return-can-i-still-make-changes/00/873608
This FAQ tells you how to save/print a copy of your tax return in TurboTax Online: https://turbotax.community.intuit.ca/community/tax-return-print-save/help/in-the-online-edition-of-turbotax-how-do-i-print-a-copy-of-my-tax-return/00/873651